Composition and method for removing copper containing scales from metals

ABSTRACT

Copper ions are complexed by any mixture of at least two compounds represented by the general formulae:   WHEREIN R1, R2, R3, and R4 are hydrogen, alkyl radicals or alkenyl radicals; R5 is a methylene group or an alkyl substituted methylene group; and R6 and R7 are hydrogen or hydroxyalkyl radicals. In another aspect copper containing scale is removed from ferrous metal surfaces with an aqueous solution comprising the above described mixture of compounds.

AU 165 E United States Patent 1 Knox et a1.

1 1 *Apr. 9, 1974 1 1 COMPOSITION AND METHOD FOR REMOVING COPPER CONTAINING SCALES FROM METALS [75] Inventors: John A. Knox; John A. Smith, both of Duncan, Okla; Roy F. Stout, deceased, late of Duncan, Okla; Richard E. Dixon, executor, Duncan, Okla.

[73] Assignee: I-Ialliburton Company, Duncan,

Okla.

[ 1 Notice: The portion of the term of this patent subsequent to May 1, 1990, has been disclaimed.

[221 Filed: Apr. 27, 1972 211 App1.No.:248,136

Related US. Application Data [60] Division of Ser. No. 248,227, April 27, 1972, Pat. No. 3,730,901, and a continuation-in-part of Ser. No. 138,410, April 29, 1971, abandoned. and a continuation-in-part of Ser. No. 56,987, July 6, 1970, abandoned.

[56] References Cited UNITED STATES PATENTS 2,959,555 11/1960 Martin et a1. 252/149 3,547,697 IZ/197tl Frost ct all. 134/3 3,579,447 5/1971 Muzyczko ct ul 252/149 X 3,585,142 6/1971 Muzyczko et a1 2. 2/87 3,686,123 8/1972 Hiroshi 252/87 3,730,901 5/1973 Knox et a1. 252/180 Primary Examiner-Mayer Weinblatt Attorney, Agent, or Firm-Thomas R. Weaver; James E. Cockfield; John H. Tregoning 57] ABSTRACT Copper ions are complexed by any mixture of at least two compounds represented by the general formulae:

and

wherein R,, R R and R, are hydrogen, alkyl radicals or alkenyl radicals; R is a methylene group or an alkyl substituted methylene group; and R and R are hydrogen or hydroxyalkyl radicals.

In another aspect copper containing scale is removed from ferrous metal surfaces with an aqueous solution comprising the above described mixture of compounds.

24 Claims, No Drawings COMPOSITION AND METHOD FOR REMOVING COPPER CONTAINING SCALES FROM METALS This application is a continuation-in-part of application Scr. No. 56,987, filed July 6, 1970 now abandoned.

This application is also a continuation-in-part of application Ser. No. l38,4l0, filed Apr. 29, l97l, and now abandoned. The present application also comprises a division of concurrent application Ser. No. 248,227, filed Apr. 27, 1972, now US. Pat. No. 3,730,901, designating John A. Knox, John A. Smith, and Roy F. Stout as co-inventors, and assigned to the assignee of the present application.

This invention relates to compositions for complexing copper ions. This invention also relates to compositions and methods for removing copper and copper compounds from a metal surface. It further relates to compositions and methods for removing copper, copper compounds, and iron oxide deposits from metal surfaces. This invention still further relates to the simultaneous removal of iron oxide scales and copper containing deposits from ferrous metal surfaces.

ln the operation of certain types of equipment, de-

' posits containing copper, its oxides, and iron oxide frequently accumulate on the surface of the equipment. Where these deposits interfere with the efficient operation of the equipment they are removed. In recent years, it has been preferred to remove the deposits chemically; that is, chemicals which dissolve the deposits are utilized.

Some solvents utilized to dissolve the deposits include aqueous solutions of certain acids. Thus when aqueous solutions of many acids are brought into contact with ferrous metal surfaces on which there is deposited copper metal and iron oxide, the iron oxide is ordinarily dissolved but the copper deposit is frequently not removed from the metal surface. Where the deposit contains an oxide of copper, it is ordinarily dissolved by the acid, but metallic copper will plate, i.e., redeposit, from the acidic solution on the ferrous metal surface. Thus the acid alone does not completely remove the offensive deposit and a second step has been required to remove the copper.

Accordingly, there has been developed in the art a one-step method for removing the aforementioned deposits whereby a removal solution capable of simultaneously removing iron oxide, copper, and copper oxide is utilized. This solution is comprised of a solvent component to dissolve, i.e., ionize, the deposit, and a second component which is capable of preventing dissolved copper, i.e., copper ions, from depositing on a ferrous metal surface in contact with the removal solution. This second component has been referred to in the art, and will be referred to herein, as a copper complexor.

When it is desired to remove metallic copper from a ferrous metal surface by a chemical solution, the solution, in addition to having copper complexing ability, should possess the capability to convert the copper metal to the ionic form. This conversion capability is referred to herein as oxidation." The oxidation capability may be inherent in the solvent component of the solution or it may be acquired by the solution through the intervention of a substance exteriorally added or produced by the solution reaction with a portion of the deposit itself.

In connection with the removal of the deposits, certain known copper complexors have been utilized individually with acidic solutions to facilitate the one-step removal of the copper and iron oxide from ferrous metal surfaces. However, whenever the copper complexor-to-copper weight ratio is low, many of the known copper complexors form an undesirable curdy, adhesive precipitate which may ultimately seriously damage the equipment sought to be cleaned. Thus, although some of the known copper complexors are effective in initially maintaining copper in solution, they can ultimately allow insoluble copper complexes to be redeposited upon the equipment surface before the cleaning operation is finished when excessive quantities of copper are present. Such redeposition is generally undesirable in industrial cleaning and can cause heat transfer irregularities such as hot spots" in industrial boilers.

Presently used copper complexors require relatively high weight ratios of copper complexor-to-copper in order to satisfactorily remove copper incrustations without forming the above mentioned undesirable precipitate. Compositions and methods have thus been sought which would permit the use of lower weights of copper complexor per unit weight of copper to be removed without the occurrence of replating and without the formation of the undesirable precipitate. Thiourea, l,3-diethyl thiourea, ethylene thiourea, monomethyl thiourea, and monoethyl thiourea are known to possess copper complexing ability; however, these complexors tend to form the undesirable curdy, adhesive precipitates when an insufficient weight of copper complexor per unit weight of copper is used.

Other known copper complexors are hexahydropyrimidine-Z-thione, N-(2-hydroxyethyl)-ethylene thiourea, diethanol thiourea, and methylimidazolidine-2-thione. Although this latter group of copper complexors avoids the problems of replating' and the formation of an undesirable precipitate, they require the use of relatively high copper complexor-to-copper weight ratios.

These and other problems are solved by the present invention which provides a composition and method for complexing copper ions.

Accordingly, we have discovered a composition consisting essentially of a mixture of at least two compounds, which composition acts to complex copper ions to a degree not to be expected nor predicted from the complexing ability, when acting alone, of the individual compounds utilized in the mixture.

In another aspect we have discovered a cleaning solution for the simultaneous removal of iron and copper deposits from metal surfaces comprising a solvent for dissolving the deposits and a copper complexor for preventing dissolved copper from forming new deposits on the metal surface, wherein the copper complexor is the above referred to composition of this invention which consists essentially of a mixture of at least two compounds.

ln still another aspect of this invention, there is provided a method for the simultaneous removal of copper and iron deposits from a ferrous metal surface.

The cleaning solution of this invention effectively removes iron and copper deposits from ferrous metal surfaces without forming a curdy, adhesive precipitate, and without plating of dissolved copper from the cleaning solution on the metal surface. Furthermore, the

In formula (1) above, R,, R R and R are hydrogen, straight or branched chain alkyl radicals having in the range of l to 3 carbon atoms, alkenyl radicals having in the range of2 to 3 carbon atoms or mixtures thereof. in formula (2) above, R is a methylene group, i.e. a Cl-l group, having 2 to 4 and preferably 2 to 3 carbon atoms, i.e. m is an integer having a value in the range of 2 to 4, preferably 2 to 3, a

group wherein n is an integer having a value in the range of O to 3 and preferably l to 2, a

group; R and R are hydrogen, a -CH CH OH group or mixtures thereof.

In one preferred embodiment, at least one of the R R R and R groups in the above formula (l), and at least one of the R and R groups in the above formula (2) are hydrogen.

In another preferred embodiment, each of the R and R groups in formula (1), and each of the R and R, groups in formula (2) is hydrogen.

Compounds believed to be useful herein which are within the scope of formula (l) above include but are not limited to:

Thiourea Monomethyl thiourea l,3-dimethyl thiourea tetramethyl thiourea monoethyl thiourea l,3-diethyl thiourea triethyl thiourea mono-n-propyl thiourea l,3-di-n-propyl thiourea l, l -di-n-propyl thiourea monoisopropyl thiourea l,3-di-isopropyl thiourea monovinyl thiourea l,3-divinyl thiourea monoallyl thiourea l-methyl-3-vinyl thiourea l-methyl-3-allyl thiourea From the above list of compounds, those which are currently preferred for use herein are:

thiourea monomethyl thiourea l,3-dimethyl thiourea monoethyl thiourea l,3-diethyl thiourea Compounds believed to be useful herein which are 10 within the scope of formula (2) above include but are not limited to:

Ethylene thiourea N-(2-hydroxyethyl)-ethylene thiourea hexahydropyrimidine-Z-thione l ,3-di( 2-hydroxyethyl )-hexahydropyrimidine-2- thione tetramethylenc thiourea l-( Z-hydmxyethyl )-tetramethylene thiourea ethylidene thiourea l-(2hydroxyethyl)-ethylidine thiourea 4-methylimidazolidine-2-thione l-(2-hydroxyethyl)-5-methylimidazolidine-2-thione 4-methylhexahydropyrimidine-Z-thione l,3-di( 2-hydroxyethyl)-4-methylhexahydropyrimidine-2-thione 4-methyl-(tetramethylene) thiourea l,3-di-( Z-hydroxyethyl )-4-methyl(tetramethylene) thiourea.

From the above list of compounds, those which are currently preferred for use herein are:

Ethylene thiourea N-(2-hydroxyethyl)-ethylene thiourea hexahydropyrimidine-2-thione 4-methylimidazolidine-Z-thione In the mixture of compounds of the composition of this invention all of the compounds in any given mixture are within the scope offormula (l) and/or formula (2); all can be from formula (1), all can be from formula (2), or some can be from formula (I) and some from formula (2).

The maximum quantity of any single given compound present in the mixed copper complexor composition of this invention is not greater than about 90, and preferably not greater than about 80, parts by weight per parts by weight of the mixture with the remaining 10 to 20 parts by weight being divided among the other compounds present in the mixture. As previously stated, the mixed copper complexor composition of this invention contains at least two compounds; however, there is no presently known maximum number of such compounds which can be included in the mixture. It is preferred, however, that any given single mixed copper complexor composition contain in the range of at least two and preferably not greater than about 10 compounds, wherein no single one of such compounds is present in the mixture in an amount greater than about 90, and preferably than about 80, parts by weight per 100 parts by weight of the mixture. In a still further preferred embodiment, the minimum quantity of any single given compound is not less than 5, and preferably not less than l0, parts by weight per 100 parts by weight of the mixture. Although it is contemplated that the mixture shall contain only those compounds which are within the scope of formula l and/or formula (2) it is to be understood that trace quantities of materials and compounds both within and without the scope of formulas (l) and (2) can be present in the mixture without departing from the spirit or scope of the composition of this invention.

Accordingly, in the preferred embodiments, twocomponent mixtures have extreme composition limits for a single component of about 80 to about 20 parts by weight per 100 parts by weight of the mixture. Thus, for example, in the mixture thiourea plus hexahydropyrimidine-2-thione, thiourea is preferably present in the range of about 80 to 20 parts by weight per 100 parts by weight of the mixture and hexahydropyrimidine-2-thione is preferably present in the range of about 20 to 80 parts by weight per 100 parts by weight of the mixture.

Still further in the preferred embodiments, compositions having more than two but not greater than about compounds in the mixture have an extreme composition limit for a single component of not greater than 80 parts by weight per 100 parts by weight of the mixture, with the other parts by weight of the mixture being divided either equally of unequally among the remaining two to about 9 compounds in the mixture. Thus, in one extreme a three-component mixture can have 80 parts by weight of one compound with the remaining 20 parts by weight being divided either equally or unequally between the two other compounds in the mixture.

It has been previously stated that the above described mixed copper complexor composition of this invention is useful to complex copper ions. Accordingly, copper dissolved in any solution is complexed by merely adding to the copper ion-containing solution the composition of this invention. In this regard there is no known quantity of copper complexor required to complex a given amount of copper except that as dictated by economics. However, it is considered that a reasonable quantity of complexor of this invention is in the range of about 2 to 50 parts by weight per one part by weight of copper to be removed.

It is believed that the composition of this invention can complex copper dissolved in other than acidic solutions; however, it is preferred that the pH of the solution is, or is adjusted to about 5 or less.

As previously stated, this invention also provides an aqueous cleaning solution for the simultaneous removal of iron and copper deposits from metal, particu' larly ferrous metal, surfaces. The cleaning solution of this invention is comprised of a solvent for the iron and copper deposits, the mixed copper complexor composition described above, and water; the solvent is present in the cleaning solution in the range of about 0.5 to 50 percent by weight of the solution and the copper complexor of this invention is present in the cleaning solution in the range of about 0.1 to 5, preferably 0.2 to 4, and still more preferably 0.4 to 3, percent by weight of the solution with the remaining weight of the solution being substantially water.

The copper complexor utilized in the cleaning solution of this invention is the mixed composition described hereinabove and reference is accordingly made to that description.

The solvent useful in the cleaning solution is any acid or acidic material capable of dissolving iron and copper deposits. Suitable acids include hydrochloric acid, hydrofluoric acid, sulfuric acid, sulfamic acid, phosphoric acid and mixtures thereof, wherein hydrochloric acid is the most preferred acid for use in the present invention. Other useful acids are citric acid, acetic acid,

gluconic acid, hydroxyacetic acid, formic acid, other organic acids and mixtures thereof. The acid is preferably used in concentrations in the range of about 0.5 percent to about 30 percent by weight of the solution. Concentrations of less than about 0.5 percent tend to be ineffective in dissolving the copper-containing iron oxides, and concentrations above about 30 percent often demonstrate excessive corrosion on the ferrous surface sought to be cleaned.

Acidic materials in addition to the above named acids also include acid salts such as sodium bisulfate, sodium bifluoride, mono-sodium citrate, potassium bisulfate, and the like.

The preferred acids and quantities in percent by weight of cleaning solution are hydrochloric acid, 3 to 10 percent; sulfuric acid, 5 to 15 percent; sulfamic acid, 3 to 10 percent; and phosphoric acid, 10 to 25 percent.

In a presently preferred embodiment the cleaning solution of this invention is comprised of one of the above named preferred acids, particularly hydrochloric acid, as the solvent, and a two-component, mixed copper complexor composition wherein one of the components is thiourea, present in the mixture in the range of about to 20, preferably 40, parts by weight per parts by weight of mixture, and the second component is hexahydropyrimidine-Z-thione, present in the mixture in the range of about 20 to 80, preferably 60, parts by weight per 100 parts by weight of mixture. In this presently preferred embodiment the concentration of copper complexor in the cleaning solution while being within the scope of the previously mentioned concentration ranges is sufficient to provide a weight ratio of complexor to copper to be removed of at least 4 to l and preferably 8 to 1.

Because in some instances there is a tendency to experience corrosiveness of the acid cleaning solution with respect vto the ferrous metal surface, it is frequently necessary to use a corrosion inhibitor as an optional element of the composition of the present invention. Any commercially available corrosion inhibitor may be used which is suitable for the acid selected. Such inhibitors are ordinarily used in amounts in the range of 0.01 to 1.0 percent by volume of the cleaning solution.

It has been found that an oxidant present in the aqueous acid solution greatly increases the rate at which the copper becomes available to the complexor. It is believed the oxidant transforms the metallic copper to ionic copper (cuprous). The oxidant may be the ferric ions which occur naturally in the iron incrustations on the ferrous metal surface sought to be cleaned, oxygen in the aqueous acid solution, or any other oxidant capable of changing the elemental copper to cuprous ions.

It has been found that the components of the present invention do not interreact chemically with each other prior to removing the copper. However, when the complexor of this invention is used, a mixed complex is formed with copper which is different from the reac- I tion product formed with copper when only one component is used. The mixed complex formed with copper and the complexor of this invention has been found to have a different crystalline structure than the reaction produce formed with copper when only one component is used.

The metal surface to be cleaned is contacted by the cleaning solution of this invention by any suitable method, e.g., soaking, pouring, spraying, circulating, and the like. The cleaning solution of this invention is trate our invention, but are not to be construed to in particularly suitable for cleaning the inside of vessels of in all of the examples which follow, the individual complex shapes where formation of a curdy, adhesive complexors utilized are identified by the capital letters precipitate can present difficult removal problems. A through I, inclusive. The following list sets out the Normally, the area to be cleaned is contacted by filling complexor and the letter by which it is identified: the vessel with the cleaning solution of this invention. A Thiourea It is found that copper removal can be particularly en- 10 B Monomethyl Thiourea hanced by stirring or other suitable means of agitation C Monoethyl Thiourea during the contacting step. D Hexahydropyrimidine-Z-thione During the contacting step, the temperature of the E N-(2- yd o y yU- y Thiourea solution is maintained in the range of 50 to 175F, and F Ethylene Thiourea preferably 120 to 160F, for a period of time sufficient G 4-Methylimidazolidine-2-thione to dissolve the deposits. This time is generally in the H 1,3 Dielhyl Thiourea range of from about 2 to 12, preferably about 4 to 8 I .3 Dim thyl Thiourea hours.

it has also been discovered that the corrosion rates of EXAMPLE I normally inhibited hydrochloric acid on ferrous metal On -half gram of copper complexor is dissolved in surfaces sought to be lean d e r d d wh th about 85 milliliters of distilled water. The resulting coppreferred concentration of the composition of the presper complexor solution is titrated with an acid solution ent invention is used as compared with corrosion rates onta ning cuprous Chloride. demonstrated by the acid when l00 percent hexahy- The acid titrating solution is prepared by dissolving dropyrimidine-Z-thione or l00 percent thiourea is in concentrated reagent grade hydrochloric acid (37.5 used. parts by weight HCl per 62.5 parts by weight water) An advantage of the copper complexor of the present about 0.006 grams cuprous chloride per milliliter of the invention is that a lower ratio of mixed complexor-toconcentrated acid. copper can be used without the formation of any pre- The titration is conducted in a 200 milliliter Berzelius cipitate than was previously possible. tall form beaker at l50F with stirring to a turbid end- An additional advantage of the mixed copper compoint which is reached when a thermistor temperature plexor of the present invention is that it provides copsensor placed in approximately the middle of the beaper removal at a surprisingly lower ratio of complexor lter within the titrated solution can no longer be seen. used to copper removed than was previously available.

Results of the titration are set out in Table l below.

Still another advantage of the mixed copper com- In Table l the total weight of complexor utilized, plexor of the present invention is that when insufficient whether singly or in admixture, is shown to be constant amounts of the mixed complexor are used, the precipiat 0.5 grams for each run. in those runs where more tate formed is dispersed and easily pumpable, in conthan one complexor is indicated, then the individual trast with the curdy, adhesive precipitate formed when complexors are present in each mixture in equal insufficient amounts of some individual thiourea derivweights. atives are used. The above general rule, however, does not hold with Also, an advantage of the mixed copper complexor respect to runs 12, 13, l5, 16, 37, 38, 39 and 40. Acof the present invention is that, in its preferred embodicordingly, in run 12 there are 0.4 grams A ment, the complexor will not replate copper when used ((0.8)(0.5)=0.4), and 0.1 grams D ((0.2)(0.5)=0.2); in a copper complexor-to-copper ratio ofat least about in run 13 there are 0.3 grams A, and 0.2 grams D; in 4;], run 15 there are 0.2 grams A, and 0.3 grams D; and in An additional advantage of the mixed copper comrun l6 there are 0.1 grams A, and 0.4 grams D. in runs plexor of the present invention is that it provides re- 37, 38, 39 and 40 the weights of complexors A and D duced acid corrosion of the ferrous surface sought to are constant at 0.135 grams and 0.2 grams respectively, be treated. and the weights of complexors C, F, B, and G are con- The following examples are provided to further illusstant at 0.165 grams.

m I0. C(IIPLEXOR CuCL-HCL cu+ act. n 0 'cmruzxox sow-non in uuo Coqtoaltion Quantity Sal'n T0001 It I by It. complexor Copper G.- .1 m GIL 2: G.- cw,- HCL ,0 Actull Predicted lAltll'.

II 90. cannon CuCL-IICL IICL he I]. h 2

I I 0.5 0.7 0.0335 3.000 9 4+0 0.5 27.7 0.1000 12.310 10 4+0 0.5 20.3 0.1013 11.000 11 4+: 0.5 17.2 0.0002 7.044 12 0.049040 0.5 21.9 0.0043 9.732 13 0.0A+0.4n 0.5 23.9 0.0920 10.021 14 0.54+0.50 0.5 27.2 0.1047 12.000 15 04490.00 0.5 24.0 0.0955 11.021 10 19.24-00.00 0.5 20.1 0.0774- 0.92 17 0+1 0.5 22.2 0.0055 9.000

41 uromvmw 0.5 25.9 0.0997 11.510

Table l above clearly shows that the weight of mixed complexor actually required to complex copper without significant precipitate formation is unexpectedly lower than the weight which would be predicted from the complexing ability of each individual complexor in the mixture when acting alone.

EXAMPLE ll Cleaning solutions consisting of various copper complexors, hydrochloric acid, an acid corrosion inhibitor. and water are prepared by mixing the above components together in the amounts set out in Table ll-A below.

'unlinuvd 2 0 common sowrrou in 24210 20041 W. I y 0 -0 9 1 Comma G Cm! NC!- "10 Actual Predicted Each cleaning solution is then placed in a 2V2-inch nominal diameter by 4-inch long mild steel pipe nipple (ASTM A53) having a rubber stopper in one end and being open on the other end. Each pipe is previously plated on the inside surface thereof with copper, and treated in a steam atmosphere at 900 to 1,000F for approximately 1.5 hours in order to also form iron oxide on the inside surface of the pipe. Accordingly. the inside of each pipe is encrusted with iron oxide and copper. The weight of copper plated on each pipe and the complexor-to-copper weight ratio for each solution is set out in Table "-8 below.

TABLE ll-A CLEANlNG SOLUTION SOLN SOLN COM- HCL 11,0 '7 7; 1

PLEXOR NO. in COM- HCL 11,0

PLEXOR Gms Gms" Gms Gms By Wt By Wt B) Wt Each solution contains 0.48 ml acid corrosion inhibitor which is the reaction product ofa rosin mine with aldehyde and a ketone plus an acetylenic alcohol plus a polyelhoxylaled alkyl phenol. "See Table ll-( for the specific complexor) utilized in each run.

TABLE ll-B 7 s2 43 l s 11 31 3s 9 1 12 4 SOLUTION COPPER WT RATIO 1 A+ 100 81 71 No. PLATE, Gms COMPLEXOR ll AIM-16D I00 92 79 COPPER l2 A+E 86 48 42.5

13 A+F 99 92 59 14 A+G 100 80 61 I 0.2 I011 20 15 A+H 86 81 57 2 0.24 6:! 1e B+C 92 81 7s 3 0.24 7:1 17 n+1) 100 91 71 18 B+E 62 34.5 19 [HF 100 66 5e 20 9+0 98 a9 53 The cleaning solution is maintained in each nipple at 2:3 38 8 :2 150F with gentle stirring for 5 hours after which time 23 C+E 7 59 495 the solution is analyzed for dissolved copper. g; 82 3 2; The actual quantity of copper removed from the nip- 26 c+1-1 74 69 64 ple by the cleaning solution is reported in Table ll-C :3 23- below in terms of the weight percent of copper origi- 30 29 D+H 93 92 57 nally plated on the nipple. Also set out in Table ll-C, Z; 3; :1 for purposes of comparison, is the weight percent of 32 F+H 77 62 37 v 3.3 0+ 914 57 39 copper wh1ch would be predicted to be removed based 34 A+D+B 94 89 7 on the removal ab1l1ty of solution contammg only one 35 35 A-l-D+C 99 90 83,6 3s A+D+F 9s 77 65.8 complexor acting alone. 37 A+D+G 97 85 I In Tables ll-A and Il-C the total we1ght of complexor 3s E+F+G 62 53 29.3 utilized, whether singly or in admixture. is shown to be 39 A+B+C+D+E+F+G+H 86 constant for each solution, i.e., solution 1, 2.4 grams; solution 2, 1.44 grams; solution 3, 1.68 grams. in those 40 3 runs where more than one complexor is indicated, then I I the individual complexors are present in each mixture Table {move l y Shows thal the Cleaning solutrons contammg a m1xture of complexors generally rem equal welghts' move sur risin l more lated coo er than would b The above general rule, however, does not hold with p g y p pp e H 34 35 36 nd 37 Accordin l in predicted from the removal ability of the 1nd1v1dual respect to P a g complexors in the mixture when acting alone. run l 1, solution 1, there are 0.96 grams Complexor A and 1.44 grams of Complexor D; and in solution 2 there EXAMPLE III are 0576 grams Of Complexor A and 0-864 grams Of Cleaning solutions consisting of various solvents, cor- Complexor 34, 1 and 1 complexors 5O rosion inhibitors compatible with the particular sol- A and D are present in constant weights in solution 1 vent, water, and a mixed copper complexor consisting at 0.648 grams and 0.96 grams respectively, and in soof 40 parts by weight thiourea per 100 parts by weight lution 2 at 0.3888 grams and 0.576 grams respectively. of the mixture and parts by weight of hexahy- Complexors B, C, F, and G are present in equal weights 'fpy P i Parts y Wfiight Of in runs 34, 35, 36, and 37 of 0.792 grams in solutions 55 mlxwre, a P p y e the abqve components 1 and 04752 grams in solutions together 1n the concentrauons set out in Table Ill below.

Each cleaning solution is then placed in a 2%-inch TABLE LC nominal diameter by 4-inch long mild steel pipe nipple (ASTM A-53) having a rubber stopper in one end and COPPER SCALE REMOVED being open on the other end. Each pipe 15 prevlously pl- Run COMPLEXOR Solution 1 Solution 2 ated on the 1ns1de surface thereof with 0.12 grams of COMPOSITION PMICM copper and thereafter treated in a steam atmosphere at I A 100 79 900 to 1,000F for approximately 1.5 hours in order to 2 a e3 also form iron oxide on the inside surface of the pipe. 3 C 97 93 Accordin l the inside of each i e is incrusted with 4 D 100 79 g y p p 5 E 12 6 iron oxide and copper. The weight of mixed complexor e F 65 39 utilized in each cleaning solution is adjusted such that the complexor-to-copper weight ratio for each solution is parts by weight complexor per l part by weight copper.

Runs 1 through 13 inclusive each utilize 24 l .2 grams 1. An aqueous cleaning solution for the removal of iron oxide and copper deposits from a ferrous metal surface consisting essentially of an acidic solvent for said deposits and a copper complexor wherein said of cleaning solution and runs 14 and 15 each utilize 5 copper complex); i a composition consisting essen. 251-25 grams of cleaning f tially of any mixture of at least two compounds repre- Each cleaning solution contains ).l percent by vol- Semed by the generaI f m ume of the total volume of the solution of a compatible copper inhibitor. 0) Ri R,

The cleaning solution is maintained in each nipple at 10 the temperature indicated in Table III with gentle stir- R2 ring for 5 hours after which time the solution is analyzed for dissolved copper.

The actual quantity of copper removed from the nip- (2) T ple by the cleaning solution is reported in Table III l5 N l. N below in terms of the weight percent copper originally Lem-5' plated on the nipple. I

In Example III which follows, the individual solvents 9 Cc"WoundS bemg Present in said mixture utilized are identified by capital letters. The following m amount of not g i than a out 80 parts by list sets out the solvent and the letter by which it is idenwe'ght Per f by of 531d mixture wherein med: at least one of said compounds in said mixture is within 1 S di Bi lf the scope of said formula (l) and at least one of said K Ammonium Bi lf compounds in said mixture is within the scope of said L Ci Acid formula (2), and further wherein R,, R R and R, are

M 9 pans by Wight Ammonia -1. 1 Pan hydrogen, straight or branched chain alkyl radicals b i h f Ci i A id having In the range of l to 3 carbon atoms, alkenyl rad- N s lfa i A d Icals having in the range of 2 to 3 carbon atoms or mix- 0 89 parts by weight of Sulfamic Acid 6 parts Plies q i R5 is z-,. g p herein m is an b i h of Citric A id Integer havlng a value in the range of 2 to 4, a P 3 parts by weight of Sodium Bisulfate 1 part by weight of Citric Acid CcHi Q 3 parts by weight of Ammonium Bisulfate l l part by weight of Citric Acid R 94 parts b w i m f S di Bi lf 1 part group wherein n is an integer havinga value in the by weight of Citric Acid ng f 0 o 3. r a S 94 parts by weight of Ammonium Bisulfate +1 part by weight of Citric Acid loll, Oll-CIh T Sulfuric Acid, H 50 V Phosphoric Acid, H PO W Hydrofluoric Acid, HF group; and R and R are hydrogen, a -CH,CH OH Z 2 parts by weight Hydroxyacetic Acid 1 part group or mixtures thereof.

by weight Formic Acid 2. The aqueous cleaning solution of claim 1 wherein TABLE lll CLEANING SOLUTION SOLVENT 9i TREATING COPPER SOLUTION COMPOSITION QUANTITY I-l,0 wT RATIO TEMPERATURE COMPLEXOR SOLVENT REMOVED No. Gms By M By Wt By Wt COMPLEXORzCOPPER '7. By wi I I 11.4 0.49 4.73 94.78 l0:l I75 42 2 K II.4 0.49 4.73 94.78 lOzl I75 69 3 L II.4 0.49 4.73 94.72 I01] I75 43 4 M I243 0.49 5.15 94.35 lUzl I75 o9 5 N II.4 0.49 4.73 94.7Ii I01] I75 77 o O I I.4 0.49 4.73 94.7li 10:1 I40 II: 7 P II.4 0.49 4.73 94.78 I01! l75 4o 3 o I I4 0.49 4.73 94.78 lOzl 175 4a 9 R 11.4 0.49 4.73 94.78 I0-.l l75 I0 5 II.4 0.49 4.73 95.78 lilzl I 47 ll T I: 0.49 4.98 94.53 I011 I50 89 12 v 24 0.49 9.95 89.55 lOzl I50 I3 w 7.2 0.49 2.99 96.52 l():l I50 54 I4 L 7.5 0.50 2.99 96.52 l0;l 55 '15 z 7.5 0.50 2.99 96.52 ltlzl I50 23 From Table lll it is clearly seen that the mixed complexor of this invention is useful to remove copper in the presence of a number of solvents. 7

Having described our invention. that which is claimed is:

at least one of said R R R and R groups in said formula (l) is hydrogen, and at least one of said R and R groups in said formula (2) is hydrogen.

3. The aqueous cleaning solution of claim 1 wherein the pH of said solution is about 5 or less.

4. The cleaning solution of claim 1 wherein said mixture contains in the range of two to about l of said compounds.

5. The cleaning solution of claim 1 wherein the minimum quantity of any of said compounds in said mixture is about parts by weight per l00 parts by weight of said mixture.

6. The aqueous cleaning solution of claim 2 wherein said integer m in said R group has a value in the range of 2 to 3, and wherein said integer n has a value in the range of l to 2.

7. The aqueous cleaning solution of claim 1 wherein said acidic solvent is present in said solution in the range of about 0.5 to 50 percent by weight of said solution, said copper complexor is present in said solution in the range of about 0.1 to 5 percent by weight of said solution, with the remaining weight of said solution being substantially water.

8. The aqueous cleaning solution of claim 7 wherein said acidic solvent is an acid or an acidic material selected from hydrochloric acid, hydrofluoric acid, sulfuric acid, sulfamic acid, phosphoric acid, citric acid, acetic acid, gluconic acid, hydroxyacetic acid, formic acid, sodium bisulfate, sodium bifluoride, ammonium bisulfate, and mixtures thereof.

9. The aqueous cleaning solution of claim 8 wherein said at least two components are selected from thiourea, monomethyl thiourea, l,3-dimethyl thiourea, monoethyl thiourea, l,3-diethyl thiourea, ethylene thiourea, N-( 2-hydroxyethyl )-ethylene thiourea, hexahydropyramidine-Z-thione, and 4- methylimidazolidine-Z-thione.

10. The aqueous cleaning solution of claim 9 wherein said acidic solvent is hydrochloric acid present in said solution in the range of about 3 to 10 percent by weight of said solution and said copper complexor is present in said solution in the range of about 0.2 to 4 percent by weight of said solution.

11. A process for removing iron oxide, and copper containing deposits from a ferrous metal surface comprising the steps of: contacting said surface with an aqueous cleaning solution comprising an acidic solvent for said deposits and a copper complexor wherein said copper complexor is a composition consisting essentially of any mixture of at least two compounds represented by the general formulae each of said compounds being present in said mixture in an amount not greater than about 80 parts by weight per 100 parts by weight of said mixture wherein at least one of said compounds in said mixture is within the scope of said formula (I) and at least one of said compounds in said mixture is within the scope of said formula (2), and further wherein R,, R,, R and R are hydrogen, straight or branched chain alkyl radicals having in the range of l to 3 carbon atoms, alkenyl radicals having in the range of 2 to 3 carbon atoms or mixtures thereof; R is a CH,,,, group wherein m is an integer having a value in the range of 2 to 4, a

f Cll-Cll--- group wherein n is an integer having a value in the range ofO to 3, or a Cllz-(flf- Cllz group; and R and R are hydrogen, a CH,CH,OH group or mixtures thereof; maintaining said contacting step for a time and at a temperature sufficient for said solution to dissolve said deposits; and, thereafter, terminating said contacting.

12. The process of claim 4 wherein at least one of said R R R and R groups in said formula l is hydrogen, and at least one of said R and R groups in said formula (2) is hydrogen.

13. The process of claim 11 wherein the pH of said solution is about 5 or less.

14. The process of claim 11 wherein said mixture contains in the range of two to about 10 of said compounds.

15. The process of claim 11 wherein the minimum quantity of any of said compounds in said mixture is about 5 parts by weight per 100 parts by weight of said mixture.

16. The process of claim 12 wherein said integer m in said R group has a value in the range of 2 to 3, and wherein said integer n has a value in the range of l to 2.

17. The process of claim 16 wherein said acidic solvent is present in said solution in the range of about 0.5 to 50 percent by weight of said solution, said copper complexor is present in said solution in the range of about 0.1 to 5 percent by weight of said solution, with the remaining weight of said solution being substantially water.

18. The process of claim 17 wherein said acidic solvent is an acid or an acidic material selected from hydrochloric acid, hydrofluoric acid, sulfuric acid, sulfamic acid, phosphoric acid, citric acid, acetic acid, gluconic acid, hydroxy-acetic acid, formic acid, sodium bisulfate, sodium bifluoride, ammonium bisulfate, and mixtures thereof.

19. The process of claim 18 wherein said acidic at least two compounds are selected from thiourea, monomethyl thiourea, l,3-dimethyl thiourea, monoethyl thiourea, l,3-diethyl thiourea, ethylene thiourea, N-( 2-hydroxyethyl )-ethylene thiourea, hexahydropyramidine-2-thione, and 4-methylamidazolidine-2- thione.

20. The process of claim 19 wherein said solvent is hydrochloric acid present in said solution in the range of about 3 to 10 percent by weight of said solution and said copper complexor is present in said solution in the range of about 0.2 to 4 percent by weight of said solution.

21. The process of claim 20 wherein said time is in the range of 2 to 12 hours and said temperature is in the range of 50 to lF.

22. The process of claim 21 wherein said cleaning solution is agitated during said contacting step.

23. The process of claim 18 wherein said at least two ride, ammonium bisulfate, and mixtures thereof. compounds are thiourea and hexahydropyramidine-2- thione and said solvent is selected from hydrofluoric acid, citric acid, acetic acid, gluconic acid, hydroxyacetic acid, formic acid, sodium bisulfate, sodium bifluo- 24. The process of claim 23 wherein said ferrous metal surface is the interior surface of a boiler.

1 2 3 UNITED STATES PATENT OFFICE 7 CERTIFICATE OF CORRECTION Patent No. 3 803 042 Dated April 9 1974 Inventor s John A. Knox, John A. Smith, Roy F. Stout It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

At Column 3, lines 17 through 20, delete the formula which reads i f CR J and insert therefor \eLN LR l

At Column 5, line 20, delete the word "of" and insert therefor or-.

At Column 5, lines 33 and 34, insert the word maximum between the words "known" and "quantity".

At Column 8, line 46, delete the numeral "2" (second occurrence) and insert the number l-.

At Column '13, TABLE III, under the Column entitled "CLEANING SOLU- 'I'ION" delete the title of the sub-column "H 0 By wt" d i t H 0 By Wt-- therefor.

At Column 13, TABLE III, in the sub-column entitled H 0 By Wt" delete the figure "95.78" reflected for Solution No. 10 and insert -94.78- therefor.

FORM (10-59) USCOMM-DC wan-ps9 I \LS. GOVERNMENT PRINTING OFFICE "8O 0-366-334,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,803,042 Dated April 94 1974 Inventor) John A. Knox, John A. Smith, Roy F. Stout PAGE 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

At Column 14, lines 14 through 17, delete the formula which reads Elf CAT At Column 15, line 1 of Claim 7, delete the number "1" and insert -6 therefor.

At Column 15, line 2 of Claim 9, delete "components" and insert --compounds-- therefor.

At Column 16, line 1 of Claim 12, delete the number "4" and insert --ll therefor.

At Column 16, line 1 of Claim 19, delete the word "acidic".

At Column 16, line 1 of Claim 20, insert --acidic-- between the words "said" and "solvent".

Signed and sealed this 13th day of August 1974.

(SEAL) Attest:

MCCOY 4. GIBSON, JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC4050 (10 69) USCOMM DC 03764369 us, covzmmzm' vmu'rmc orncr: II" o-su-Ju. 

2. The aqueous cleaning solution of claim 1 wherein at least one of said R1, R2, R3, and R4 groups in said formula (1) is hydrogen, and at least one of said R6 and R7 groups in said formula (2) is hydrogen.
 3. The aqueous cleaning solution of claim 1 wherein the pH of said solution is about 5 or less.
 4. The cleaning solution of claim 1 wherein said mixture contains in the range of two to about 10 of said compounds.
 5. The cleaning solution of claim 1 wherein the minimum quantity of any of said compounds in said mixture is about 5 parts by weight per 100 parts by weight of said mixture.
 6. The aqueous cleaning solution of claim 2 wherein said integer m in said R5 group has a value in the range of 2 to 3, and wherein said integer n has a value in the range of 1 to
 2. 7. The aqueous cleaning solution of claim 1 wherein said acidic solvent is present in said solution in the range of about 0.5 to 50 percent by weight of said solution, said copper complexor is present in said solution in the range of about 0.1 to 5 percent by weight of said solution, with the remaining weight of said solution being substantially water.
 8. The aqueous cleaning solution of claim 7 wherein said acidic solvent is an acid or an acidic material selected from hydrochloric acid, hydrofluoric acid, sulfuric acid, sulfamic acid, phosphoric acid, citric acid, acetic acid, gluconic acid, hydroxyacetic acid, formic acid, sodium bisulfate, sodium bifluoride, ammonium bisulfate, and mixtures thereof.
 9. The aqueous cleaning solution of claim 8 wherein said at least two compounds are selected from thiourea, monomethyl thiourea, 1,3-dimethyl thiourea, monoethyl thiourea, 1,3-diethyl thiourea, ethylene thiourea, N-(2-hydroxyethyl)-ethylene thiourea, hexahydropyramidine-2-thione, and 4-methylimidazolidine-2-thione.
 10. The aqueous cleaning solution of claim 9 wherein said acidic solvent is hydrochloric acid present in said solution in the range of about 3 to 10 percent by weight of said solution and said copper complexor is present in said solution in the range of about 0.2 to 4 percent by weight of said solution.
 11. A process for removing iron oxide, and copper containing depOsits from a ferrous metal surface comprising the steps of: contacting said surface with an aqueous cleaning solution comprising an acidic solvent for said deposits and a copper complexor wherein said copper complexor is a composition consisting essentially of any mixture of at least two compounds represented by the general formulae
 12. The process of claim 4 wherein at least one of said R1, R2, R3, and R4 groups in said formula (1) is hydrogen, and at least one of said R6 and R7 groups in said formula (2) is hydrogen.
 13. The process of claim 11 wherein the pH of said solution is about 5 or less.
 14. The process of claim 11 wherein said mixture contains in the range of two to about 10 of said compounds.
 15. The process of claim 11 wherein the minimum quantity of any of said compounds in said mixture is about 5 parts by weight per 100 parts by weight of said mixture.
 16. The process of claim 12 wherein said integer m in said R5 group has a value in the range of 2 to 3, and wherein said integer n has a value in the range of 1 to
 2. 17. The process of claim 16 wherein said acidic solvent is present in said solution in the range of about 0.5 to 50 percent by weight of said solution, said copper complexor is present in said solution in the range of about 0.1 to 5 percent by weight of said solution, with the remaining weight of said solution being substantially water.
 18. The process of claim 17 wherein said acidic solvent is an acid or an acidic material selected from hydrochloric acid, hydrofluoric acid, sulfuric acid, sulfamic acid, phosphoric acid, citric acid, acetic acid, gluconic acid, hydroxy-acetic acid, formic acid, sodium bisulfate, sodium bifluoride, ammonium bisulfate, and mixtures thereof.
 19. The process of claim 18 wherein said acidic at least two compounds are selected from thiourea, monomethyl thiourea, 1,3-dimethyl thiourea, monoethyl thiourea, 1,3-diethyl thiourea, ethylene thiourea, N-(2-hydroxyethyl)-ethylene thiourea, hexahydropyramidine-2-thione, and 4-methylamidazolidine-2-thione.
 20. The process of claim 19 wherein said solvent is hydrochloric acid present in said solution in the range of about 3 to 10 percent by weight of said solution and said copper complexor is present in said solution in the range of about 0.2 to 4 percent by weight of said solution.
 21. The process of claim 20 wherein said time is in the range of 2 to 12 hours and said temperature is in the range of 50* to 175*F.
 22. The process of claim 21 wherein said cleaning solution is agitated during said contacting step.
 23. The proCess of claim 18 wherein said at least two compounds are thiourea and hexahydropyramidine-2-thione and said solvent is selected from hydrofluoric acid, citric acid, acetic acid, gluconic acid, hydroxyacetic acid, formic acid, sodium bisulfate, sodium bifluoride, ammonium bisulfate, and mixtures thereof.
 24. The process of claim 23 wherein said ferrous metal surface is the interior surface of a boiler. 